OSU's defense this year is FAR different from last year. Personnel wise, the only defensive back from last year's team is Doran Grant, first team All Big Ten. Eli Apple, Vonn Bell, and Tyvis Powell were not starters all of last season (Vonn only played real time against Clemson).
Also, the defensive scheme used last year is much different than this year. Last year, we were without Bradley Roby for the bowl game because of an injury. As a result, they just played a soft zone coverage playing far off the ball. Sammy Watkins caught about 155 bubble screens in that game against OSU. This year, with a new secondary coach, OSU plays an up front press man coverage style, which has changed results dramatically.
Look at the pass defensive numbers compared to last year and tell me it's practically the same:
http://www.teamrankings.com/college-football/stat/opponent-passing-yards-per-game
This year OSU is 11th in passing yards allowed, last year OSU was 118th. That's a huge difference.
This year OSU is 6th in defensive passer rating, last year OSU was 83rd. Again, not the same defense.